[Feature-8530][API] add system default timezone if no user timezone when get userInfo (#8899)

Co-authored-by: caishunfeng <534328519@qq.com>

dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/service/impl/UsersServiceImpl.java

@@ -66,6 +66,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.TimeZone;
 import java.util.stream.Collectors;
 
 import org.slf4j.Logger;
@@ -886,6 +887,11 @@ public class UsersServiceImpl extends BaseServiceImpl implements UsersService {
             }
         }
 
+        // add system default timezone if not user timezone
+        if (StringUtils.isEmpty(user.getTimeZone())) {
+            user.setTimeZone(TimeZone.getDefault().toZoneId().getId());
+        }
+
         result.put(Constants.DATA_LIST, user);
 
         putMsg(result, Status.SUCCESS);